1. Field of the Invention
The present invention relates to liquid crystal display (LCD) devices, and more particularly to an LCD device having photo spacers between substrates thereof.
2. Description of the Related Art
An LCD device has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD device is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
In a TFT-LCD (thin film transistor liquid crystal display) device, spacers are provided between two substrates of the device to maintain a cell gap between the substrates. The spacers may be plastic beads, glass beads, or glass fibers. Generally, the spacers are distributed onto one of the substrates during manufacturing of the device. The method of distribution may, for example, be spraying. The spacers are used to keep the cell gap consistent, so as to ensure that the device performs accurately and reliably. However, many or most of the spacers are deposited in a display region of the device. These spacers cause light scattering, which is liable to generate white point defects. Thus, the contrast and the display performance of the device are impaired. For this reason, photo spacers formed by a photolithographic process have been developed to replace conventional plastic beads, glass beads, or glass fibers. Dimensions and positions of the photo spacers are configured to avoid affecting the transmission of light, while at the same time ensuring a uniform cell gap. Thus, the display performance of the device is enhanced.
Referring to FIG. 7, this is a simplified, schematic, side cross-sectional view of a conventional LCD device having photo spacers. In the process of making the LCD device 70, firstly, a color pixel layer 174 and a black matrix layer 175 are provided on a color filter substrate 171. A continuous photo spacer 176 is formed on a peripheral region of the color filter substrate 171. The photo spacer 176 is located at an outside of the black matrix 175 and the color pixel layer 174, and is spaced a predetermined distance from the black matrix layer 175. Secondly, a sealant 177 is formed on a TFT substrate 179. The sealant 177 is located opposite to an outside of the photo spacer 176. Drops of liquid crystal 178 are dispensed onto the TFT substrate 179 one by one. Then the color filter substrate 171 is pressed face-to-face onto the TFT substrate 179 under vacuum, and the sealant 177 is cured by applying ultraviolet light thereto. The color filter substrate 171 and the TFT substrate 179 are thus engaged together to form the LCD device 70.
The black matrix and the color pixel layers 175, 174 are separated from the sealant 177 by the photo spacer 176. When ultraviolet light is applied from a top side of the color filter substrate 171 to cure the sealant 177, the black matrix layer 175 does not interfere with the irradiation of the sealant 177. In other words, there are no light shielding problems, and the sealant 177 can be completely cured. Moreover, during the curing process, the sealant 177 does not contact the liquid crystal 178, so the liquid crystal 178 cannot be soiled or damaged.
However, the photo spacer 176 is only formed at the peripheral region of the LCD device 70. Portions of the substrates 171, 179 at the black matrix and color pixel layers 175, 174, and at peripheral regions outside the sealant 177, are not directly supported by the photo spacer 176. Therefore, the distance between the substrates 171, 179 may not be uniform. That is, the LCD device 70 may not have a consistent cell gap, which can impair the display characteristics of the LCD device 70.
It is desired to provide an improved LCD device which overcomes the above-described deficiencies.